"JavaScript: The Dynamic Language of the Web"
Hello World
2. JavaScript Basics Variables and Data Types var, let, const Primitive types: Number, String, Boolean, Null, Undefined, Symbol, BigInt Example: let age = 25;
const name = "Alice";
console.log(`Name: ${name}, Age: ${age}`);
Operators
Arithmetic, Comparison, Logical, Assignment
Example:
let x = 5, y = 10;
console.log(x + y); // Output: 15
console.log(x > y); // Output: false
3. Control Structures
Conditional Statements
if, else if, else, switch
Example:
const time = 20;
if (time < 12) {
console.log("Good Morning");
} else {
console.log("Good Evening");
}
Loops
for, while, do...while, for...of, for...in
Example:
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for (let i = 1; i <= 5; i++) {
console.log(`Number: ${i}`);
} 4. Functions
Function Declaration and Expression
Arrow Functions
Example:
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// Function Declaration
function greet(name) {
return `Hello, ${name}!`;
}
console.log(greet("Alice"));
// Arrow Function
const add = (a, b) => a + b;
console.log(add(5, 10));
5. DOM Manipulation
Selecting Elements
getElementById, querySelector, querySelectorAll
Changing Content and Styles
Example:
6. Events
Event Listeners
click, mouseover, keydown, etc.
Example:
html
Asynchronous JavaScript
Callbacks, Promises, Async/Await
Example:
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const fetchData = async () => {
try {
const response = await fetch("https://jsonplaceholder.typicode.com/posts");
const data = await response.json();
console.log(data);
} catch (error) {
console.error("Error fetching data:", error);
}
};
fetchData();
8. Object-Oriented Programming (OOP)
Classes and Objects
Inheritance
Example:
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class Person {
constructor(name, age) {
this.name = name;
this.age = age;
}
greet() {
console.log(`Hello, I'm ${this.name}, ${this.age} years old.`);
}
}
const alice = new Person("Alice", 25);
alice.greet();
9. Advanced Topics
Modules
export and import
Example:
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// utils.js
export const add = (a, b) => a + b;
// main.js
import { add } from './utils.js';
console.log(add(5, 10));
Closures
Example:
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function counter() {
let count = 0;
return function () {
count++;
console.log(count);
};
}
const increment = counter();
increment(); // 1
increment(); // 2
Prototypes
Example: function Animal(name) {
this.name = name;
}
Animal.prototype.speak = function () {
console.log(`${this.name} makes a noise.`);
};
const dog = new Animal("Dog");
dog.speak();
10. JavaScript in Real-World Applications
API Integration
Building a To-Do App
Example with localStorage
Example:
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